The present invention relates to circuit board components and more particularly to electrically isolated and thermally conductive pre-packaged components.
There are numerous types of circuit board components in use today, including those which have been specifically developed for high current and high power applications, such as for electrical vehicles. A current component used in these applications is a TO247 package. These devices utilize metalized ceramic substrates, stamped copper leads or lead frames, wire bonds, or solderable topside integrated circuits (IC). There are a variety of solderable topside packages for use with discreet power devices and integrated circuits. One of these devices utilizes a plastic material to overmold the TO247 package except for the bottom surface. The plastic overmold protects the internal die and wire bonds or bond straps. The bottom surfaces in most instances are electrically attached and thermally conductive. It is typically left open to provide a thermal and electrical path out of the package. This path also allows the end user to connect the package to a heat sinking mass or an electrical bus.
With these prior devices, a heat sink pad must be added in order to achieve electrical isolation. The pad, however, adds thermal resistance to the assembly, typically on the order of 0.1 to 0.5 degrees per C/watt.
It is an object of the present invention to provide an improved circuit board component for high power and high current applications, such as an improved TO220 type-package. The TO220-type package is one half the size of a TO247 package. It is also an object of the present invention to provide a TO220-type component which has improved thermal performance and electrical isolation. It is a further object of the present invention to provide a TO220-type component which has higher current carrying capabilities than wire bonds and better durability and fatigue strength. It is a still further object of the present invention to provide a reliable, high current, high power TO220-type device that is pre-packaged and available for use in a variety of applications.
The present invention provides an electrically isolated and thermally conductive double-sided TO220-type component. The invention provides a pre-packaged component which has particular use in high current and high power applications. The component has a pair of ceramic substrates on the top and bottom sides with stamped copper leads or lead frames. Integrated circuit (IC) devices such as discrete transistors, diodes, resistors, etc. are positioned between the ceramic substrates. Solderable bonded copper layers are provided on the top and bottom ceramic substrates. Power from the device is dissipated in two directions and the temperature rise is reduced approximately in half. The electrically isolated top and bottom surfaces eliminate the use of heat sink pads.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.